You should probably reread chapter 31. I just did too, to remind myself exactly what happened.
It's very obvious that Aaron't treatment of him (demeaning,being like dur hur you're such a good slut, you love cocks, nobody's gonna fuck you as good as I do etc, suddenly deciding to extend the contract to keep him around "like a pet") triggered Eugene's trauma. He even had a flashback to a young Aaron that got triggered by that phrase.
We're missing full context but Aaron is NOT acting good to Eugene. He's obsessive, manipulative and all he talks about how his dick is a miracle.
Oooh all right,thanks for the reminder
Ok so I'm seeing a lot of people blaming Aaron as if he did something unforgivable...and I don't get itwhat exactly did he do that was so bad?I don't get why Yujin suddenly punched him either tbh